The present invention relates to a process for recovering nuclear fuel materials such as uranium (U) and plutonium (Pu) from spent nuclear fuels by utilizing phenomenon of cocrystallization of U and Pu.
Spent nuclear fuels contain materials that can be used again as nuclear fuels such as U, Pu and the like. Accordingly, energy resource can be utilized effectively by recovering and reusing these materials.
A process for reprocessing spent nuclear fuels put to practical use at present includes a Purex process. In this process, fuel assemblies are sheared at first and dissolved into nitric acid. Then, the resulting nitric acid solution is clarified, a nitric acid concentration and the like are adjusted, and U and Pu are extracted using tributyl phosphate (TBP) as an extraction solvent. Further, valence adjustment and the like are conducted by using reagents, and U and Pu are back-extracted, respectively, into an aqueous phase to selectively separate and recover U and Pu from fission products (FP), transuranium elements (TRU), corrosion products (CP) and the like.
The Purex process described above is an excellent process for reprocessing spent nuclear fuels in view of selective recovery of U and Pu, criticality control, safety, handling, etc. However, in view of reduction of the burden on the environment, it has been demanded to simplify the process steps and decrease the amount of liquid wastes generated. Further, use of an organic solvent under the presence of nitric acid may possibly form an explosive organic compound which is called “Red Oil” and therefore additional operation and control are required. Furthermore, since there is a process step in which Pu is present separately, it may be somewhat disadvantageous in view of nuclear non-proliferation.